Spectacles of this type are widely used for protecting the user's eyes from light, wind, dust and meteorological phenomena, particularly during sports activities.
Many investigations have recently been undertaken in the technical field of sports spectacles with the purpose, amongst other things, of evaluating the effect of the air-flow due to wind (both atmospheric wind and wind due to speed) on the lenses, the ventilation of the internal surfaces of the lenses in order to prevent them from misting up, interaction with the user's field of view, and yet further aspects. For example, it has been found that, regardless of whether the air which strikes the lens is due to meteorological wind or to wind resulting from "speed", it tends to pass over the spectacle frame, creating turbulence on the rear face of the lens, which is troublesome to the user.